H3N2 canine influenza virus with the matrix gene from the pandemic A/H1N1 virus: infection dynamics in dogs and ferrets.

After an outbreak of pandemic influenza A/H1N1 (pH1N1) virus, we had previously reported the emergence of a recombinant canine influenza virus (CIV) between the pH1N1 virus and the classic H3N2 CIV. Our ongoing routine surveillance isolated another reassortant H3N2 CIV carrying the matrix gene of the pH1N1 virus from 2012. The infection dynamics of this H3N2 CIV variant (CIV/H3N2mv) were investigated in dogs and ferrets via experimental infection and transmission. The CIV/H3N2mv-infected dogs and ferrets produced typical symptoms of respiratory disease, virus shedding, seroconversion, and direct-contact transmissions. Although indirect exposure was not presented for ferrets, CIV/H3N2mv presented higher viral replication in MDCK cells and more efficient transmission was observed in ferrets compared to classic CIV H3N2. This study demonstrates the effect of reassortment of the M gene of pH1N1 in CIV H3N2.

Radioimmunoassay for myeloma idiotype.

Rabbit anti-idiotype antisera were prepared against four human myeloma proteins. These antisera demonstrated a capacity to bind the 125I-labeled autologous purified monoclonal IgG, but failed to demonstrate any binding to 125I-labeled normal IgG or to labeled myeloma IgG obtained from other myeloma patients. The anti-idiotypic antisera were used with 125I-labeled autologous myeloma IgG preparations and goat antirabbit IgG for specific radioimmunoassay with a sensitivity limit of 20 ng/ml. Little or no cross-reaction occurred between these anti-idiotypic antisera and normal IgG preparations or other myeloma IgG proteins.

Specific killing of human T-leukemia cells by immunotoxins prepared with ricin A chain and monoclonal anti-human T-cell leukemia antibodies.

In this study, immunotoxins containing monoclonal anti-human T-cell leukemia antibodies are shown to be capable of specific killing of human T-leukemia cells in vitro. These immunotoxins were prepared by conjugating ricin A chain (RIA) with our recently generated murine monoclonal antibodies, SN1 and SN2, the latter of which was obtained from a hybridoma clone N6/D11 described previously by Negoro and Seon (Cancer Res., 42: 4259-4262, 1982), directed to two unique human T-cell leukemia antigens. We have shown previously that these monoclonal antibodies do not react with non-T-leukemia cells nor with various normal cells including normal T-cells, thymocytes, and bone marrow cells (Proc. Natl. Acad. Sci. U. S. A., 80: 845, 1983; Cancer Res., 42: 4259, 1982). Control conjugate was also prepared by conjugating RIA with a murine monoclonal immunoglobulin G (IgG), the isotype of which is the same as that of SN1 and SN2, i.e., IgG1-kappa. In initial experiments, the cytotoxic activity of an SN1 IgG:RIA conjugate preparation and the control IgG conjugate preparation against leukemic T-cell lines and normal B-cell lines was tested by two different test procedures, i.e., by measuring direct killing of the cells and by measuring inhibitory activity against protein synthesis in the cells. In each test, the SN1 conjugate showed specific cytotoxic activity against T-leukemia cells, whereas the control conjugate was not cytotoxic against either T-leukemia cells or normal B-cells. Nearly complete killing of T-leukemia cells and inhibition of protein synthesis in T-leukemia cells were observed at the concentrations of 10(-8) to 10(-7) M of the SN1 IgG:RIA conjugate. In subsequent experiments, another preparation of SN1 IgG:RIA conjugate and an SN2 IgG:RIA conjugate preparation were tested individually and together for their inhibitory activity against protein synthesis in T-leukemia cells and control cells. With T-leukemia cells, specific inhibition was observed for both SN1 IgG:RIA and SN2 IgG:RIA. The combined use of these conjugates did not display a synergistic effect. Nevertheless, the combined use of different immunotoxins directed to different antigen molecules will be important in clinical use, since uncultured tumor cells derived freshly from patients, in general, display heterogeneity with respect to the expression of tumor-associated antigens. These immunotoxins may be useful for the in vitro eradication of tumor cells in the bone marrow taken from patients with T-cell leukemia.(ABSTRACT TRUNCATED AT 400 WORDS)

Molecular nature of a cell membrane antigen specific for human T-cell acute lymphoblastic leukemia.

In the present work, we characterized the molecular nature of a T-cell acute lymphoblastic leukemia (T ALL) specific antigen, termed TALLA, which is defined by monoclonal antibody SN1. SN1 shows an extremely high specificity for T ALL. In the present study, SN1 was further shown not to react significantly with various normal solid tissues. TALLA was determined to be a glycoprotein with an approximate molecular weight of 150,000. However, the molecular nature of TALLA is peculiar in that heating at 100 degrees C for 2 min renders TALLA undetectable in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It should be noted that such heating is a common practice before analysis of proteins and glycoproteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. No significant antigenic modulation of TALLA was observed when T ALL cells were reacted with SN1. Two new monoclonal antibodies, SN1a and SN1b, which show the same cell binding specificity as SN1 were also generated in the present work and compared to SN1. Competitive binding experiments showed that the epitopes on TALLA recognized by SN1, SN1a, and SN1b are sufficiently close to one another to allow complete reciprocal inhibition of antibody binding. These epitopes apparently became more exposed to antibody when T ALL cells were treated with neuraminidase; neuraminidase-treated T ALL cells bind 29-35% more SN1, SN1a, and SN1b as compared to the original T ALL cells.

Strong, specific anti-human leukemia antisera prepared with the use of purified cell membrane antigen.

Two rabbits immunized with 15 micrograms of a purified human thymus leukemia-associated antigen preparation and boosted once with the same amount of the antigen preparation yielded antisera that showed strong specificity for human leukemic T-cells without any prior absorptions. These antisera from the two rabbits showed a 50% killing of cells at antiserum dilutions of 5700- and 1600-fold, respectively, against JM, a leukemic T-cell line, and slightly weaker activity against MOLT-4, another leukemia T-cell line. These antisera, without any absorption, showed no or minimal reaction against two nonmalignant B-cell lines (RPMI 1788 and RPMI 8057), a leukemic non-T, non-B-cell line (NALM-16), a leukemic pre-B-cell line (NALM-1), normal peripheral blood lymphocytes, and T-cells isolated from peripheral blood lymphocytes. Antiserum 7557, which showed the higher antibody activity, was further studied by an absorption test using various human cell lines. The antiserum showed strong activity against all three leukemic T-cell lines tested, i.e., CCRF-CEM, RPMI 8402, and CCRF-HSB-2, whereas it showed no significant activity against other cell lines which included two leukemic non-T, non-B-cell lines (KM-3 and NALM-6), NALM-1 and RPMI 1788. These are the first anti-human leukemia antisera, except for monoclonal hybridoma antibodies, that showed good specificity for leukemia cells without prior absorption. The present procedure of immunizing animals with a small amount of human thymus leukemia-associated antigen preparation isolated from cell membrane will also be useful for obtaining strong, specific antisera of other cell membrane antigens.

Several new monoclonal antibodies directed to human T-cell leukemia antigens.

Murine monoclonal hybridoma antibodies were generated efficiently by using a human leukemia antigen preparation which was isolated from the cell membranes of MOLT-4 (a T-leukemia cell line) by means of a novel system. The generated monoclonal hybridoma antibodies were screened and characterized by a radioimmunoassay using a variety of cell specimens as targets. The results showed that the antigen(s) defined by several of these monoclonal hybridoma antibodies is associated with human T-cell leukemia and further suggest that this antigen(s) is a new type of human leukemia-associated cell surface antigen.

Efficient transplantation of human non-T-leukemia cells into nude mice and induction of complete regression of the transplanted distinct tumors by ricin A-chain conjugates of monoclonal antibodies SN5 and SN6.

In the present study, we established a dependable system by which human pre-B- and non-T/non-B-acute lymphoblastic leukemia (ALL) cells are efficiently transplanted into nude mice; the transplanted tumors provide a useful model for investigating the efficacy of antitumor agents in the in vivo therapy of human cancer. NALM-6 (a pre-B-ALL cell line) cells were transplanted under varying conditions as the pre-B-leukemia cells, whereas REH (a non-T/non-B-ALL cell line) cells were transplanted as the non-T/non-B-leukemia cells. Under optimal and near optimal conditions, 71 of 101 X-irradiated mice (70%) developed distinct tumors approximately 2 wk after i.d. inoculation of a mixture of NALM-6 cells and X-irradiated human fibrosarcoma cells. Under the same conditions, 9 of 11 mice (82%) developed tumors following i.d. inoculation of REH cells admixed with X-irradiated human fibrosarcoma cells. Examination of the tumor tissues demonstrated that the tumors are of leukemia origin but not of fibrosarcoma origin. To demonstrate the usefulness of the present tumors for investigating the efficacy of antitumor agents in the in vivo therapy of human cancer, immunotoxins were tested for their specific suppressive activity against growing tumors of the transplanted NALM-6 cells. To this end, monoclonal antibodies SN5 and SN6 which define a common ALL antigen, termed CALLA, and a novel leukemia-associated cell surface glycoprotein, termed gp160, respectively, were separately conjugated with the A-chain subunit of ricin, a plant toxin; CALLA and gp160 are expressed on the cell surface of various human non-T-leukemia cells including NALM-6 cells. The conjugates of SN5 and SN6 with ricin A-chain (RA) showed specific activity against the leukemia cells but not against control cells in an in vitro assay. To investigate their in vivo efficacy in suppressing tumor growth, nude mice which had been inoculated i.d. with NALM-6 cells 25 days in advance and bore distinct palpable tumors (5 to 6 mm in diameter) were divided into five groups. One group of mice was nontreated as a control. Each of the remaining four groups of mice was given an injection of one of the following agents: (a) purified control mouse IgG (IgG1); (b) purified antibodies SN5 (IgG1) and SN6 (IgG1); (c) control IgG-RA conjugate; or (d) SN5-RA and SN6-RA. Tumors in all mice of the first four groups including the untreated group grew continuously, causing the mice to die.(ABSTRACT TRUNCATED AT 400 WORDS)

Synergistic potentiation of in vivo antitumor activity of anti-human T-leukemia immunotoxins by recombinant alpha-interferon and daunorubicin.

In the present study, immunotoxins (ITs) containing ricin A chain (RA) and anti-human T leukemia monoclonal antibodies SN1 and SN2 were used with or without alpha-interferon (IFN) and/or daunorubicin (DNR) for in vivo tumor suppression. SN1 and SN2 are directed toward two unique human T-leukemia-associated cell surface antigens, TALLA and GP37, respectively. As the tumor model, we used nude mice bearing ascitic tumors of Ichikawa, a human T acute lymphoblastic leukemia cell line. In initial studies, we investigated the effect of the IT injection schedule on the efficacy of ITs in the in vivo suppression of the ascitic tumors. Four doses of 20 micrograms each of SN1-RA and SN2-RA completely suppress the tumor growth in 100% of the treated mice when the IT treatment is initiated either 1 or 2 days after tumor inoculation of 1.6 x 10(7) Ichikawa cells into the mice. Subsequently, we investigated the potentiating effects of IFN and DNR on the in vivo antitumor activity of ITs. To this end, we chose to initiate the treatment 4 days after the tumor inoculation when IT treatment alone is only partially effective. ITs (10 micrograms each of SN1-RA and SN2-RA) plus IFN (2 x 10(5) IU) or ITs plus IFN plus DNR (5 micrograms) completely suppress tumor growth in 100% of the treated mice while similar treatment with any one of the three agents is only partially effective. Similar treatment with ITs plus DNR or IFN plus DNR results in complete suppression of tumor growth in 80% of the treated mice. These results were reproducible in a repeated experiment. To gain information about the mechanisms involving the IFN potentiation of IT activity, we carried out several experiments. The cell surface expression of TALLA and GP37 was slightly augmented by the in vitro incubation of Ichikawa cells with IFN as measured by fluorescence-activated cell sorter analysis. The degree of the increase in either TALLA or GP37 was significantly smaller than that of HLA class I antigens in the same experiment. In in vitro experiments, IFN did not show any significant cytotoxic activity against Ichikawa cells or augment the cytotoxic activity of ITs against Ichikawa cells. On the other hand, injections of IFN into nude mice augmented activity of macrophages and NK cells; however, Ichikawa leukemia cells were rather resistant to the NK cell lysis.(ABSTRACT TRUNCATED AT 400 WORDS)

Monoclonal antibody SN10 which shows a highly selective reactivity with human B leukemia-lymphoma and is effectively internalized into cells.

The monoclonal antibody termed SN10 (IgG1-k) which was generated and characterized in the present study shows a highly selective reactivity with fresh (uncultured) human leukemia-lymphoma cells. The antigen defined by SN10 is a cell surface glycoprotein composed of a single polypeptide chain of Mr 36,000 and designated as gp36. The primary reactivity of SN10 is against mature B-lineage leukemia-lymphoma cells. For instance, SN10 reacted with all of the 17 B non-Hodgkin's lymphoma specimens, all of the 15 B chronic lymphocytic leukemia specimens, both of the 2 B prolymphocytic leukemia specimens, all of the 3 B hairy cell leukemia specimens, and 2 of the 3 B acute lymphoblastic leukemia specimens tested. Of normal peripheral blood cells, only a marginal reactivity of SN10 was detected with a minor subpopulation (less than 1-4% among different specimens) of isolated B-cells from healthy donors. No significant reactivity of SN10 was detected against any other isolated normal peripheral blood cells which include T-cells, granulocytes, monocytes, erythrocytes, and platelets. Furthermore, no significant reactivity of SN10 was detected against normal bone marrow specimens. In immunohistological studies using frozen tissue sections, SN10 reacted well with malignant lymphomas and showed varying patterns of reaction with hyperplastic reactive lymph nodes. Various normal human tissues tested were unreactive with SN10. In general, glycoprotein 36 was more abundantly expressed on fresh (uncultured) leukemia-lymphoma cells than on cultured leukemia-lymphoma cell lines. No significant amount of circulating SN10 antigen was detected in the plasma of leukemia-lymphoma patients or normal healthy donors. Scatchard plot analysis of direct binding of radiolabeled SN10 to a fresh (uncultured) B non-Hodgkin's lymphoma cell specimen, a fresh B chronic lymphocytic leukemia cell specimen, and DND-39 (an American Burkitt's lymphoma cell line) showed equilibrium constants of 5.2, 5.8, and 6.8 x 10(8) liters/mol, respectively. Thus, SN10 shows a high binding avidity to each of the 3 B leukemia-lymphoma cell specimens tested. Ricin A chain conjugate of SN10 killed leukemia-lymphoma cells effectively, whereas the same conjugate showed no cytotoxicity against control cells. Thus, SN10 bound to target antigen on the cell surface was effectively internalized into the cell. The present results suggest the potential of SN10 for therapy as well as for diagnosis of various forms of leukemia-lymphoma, particularly mature B-lineage leukemia-lymphoma.

Antiangiogenic therapy of established tumors in human skin/severe combined immunodeficiency mouse chimeras by anti-endoglin (CD105) monoclonal antibodies, and synergy between anti-endoglin antibody and cyclophosphamide.

Endoglin (EDG; CD105) is a proliferation-associated cell membrane antigen of endothelial cells and is strongly expressed on the tumor-associated angiogenic vascular endothelium. Furthermore, EDG is essential for angiogenesis and a component of the transforming growth factor (TGF)-beta receptor complex. The present three anti-EDG monoclonal antibodies (mAbs), SN6f, SN6j, and SN6k, react strongly with proliferating human endothelial cells but cross-react very weakly with murine endothelial cells. Analysis of Scatchard plot of direct binding of these mAbs to proliferating human umbilical vein endothelial cells showed equilibrium constants of 8.3 x 10(9), 3.1 x 10(9), and 1.0 x 10(9) liter/mol, respectively, for SN6f, SN6j, and SN6k. These mAbs did not react with MCF-7 human breast cancer cells. To facilitate antiangiogenic tumor therapy by these mAbs in animal models, we used human skin/severe combined immunodeficiency (SCID) mouse chimeras bearing tumors of MCF-7. Blood vessels in the chimeras were analyzed by immunostaining with species (human or mouse)-specific anti-CD31 and anti-EDG mAbs including an antihuman EDG mAb termed SN6h. Blood vessels in the completely healed grafted human skins consisted of a mixture of human (43.5%) and murine (56.5%) vessels, whereas only murine vessels were detected in the adjacent murine skins and s.c. tissues. Therefore, murine vessels infiltrate into the human skin grafts from the adjacent murine tissues, whereas the growth of human vessels is limited within the boundary of human skins. Growth of human MCF-7 tumors in the human skin grafts increased the ratio of human:murine vessels. Analyses of the grafted skins before and after tumor transplantation showed that SN6h reacted with tumor-induced angiogenic blood vessels but not with nonangiogenic vessels, whereas antihuman CD31 mAb reacted with both angiogenic and nonangiogenic vessels. The results show that SN6h is capable of distinguishing the tumor-induced angiogenic vasculature from the nonangiogenic vasculature in the present model. Antiangiogenic therapy of the chimeras bearing established MCF-7 tumors was carried out by i.v. administration of a mAb(s) via the tail vein of mice. SN6j and SN6k were effective for suppressing the established tumors, whereas tumor suppression was weaker with SN6f. The results indicate an absence of a direct correlation between antigen-binding avidity and in vivo antitumor efficacy of anti-EDG mAbs and suggest the importance of other factors (e.g., epitopes) in antitumor efficacy. No significant toxicity of the mAbs was detected. Combination of SN6f and SN6k that define mutually nonoverlapping epitopes showed an additive antitumor effect. Combination of SN6j and cyclophosphamide using an antiangiogenic schedule of drug dosing showed synergistic antitumor efficacy. The combination therapy induced lasting complete regression of the established tumors in two of the eight treated chimeras. We examined human and murine blood vessels in large human tumors from the chimeras at the end of therapeutic experiment. The test showed that SN6j therapy resulted in complete suppression of human vessels in the tumors but resulted in only weak suppression of murine vessels. Cyclophosphamide was not effective for suppressing human vessels and only weakly suppressive against murine vessels. Combination of SN6j and cyclophosphamide was effective for completely suppressing human vessels and also effective for partial (i.e., 35%) suppression of murine vessels. The results show that systemic administration of naked antihuman EDG mAbs can suppress established tumors, and the efficacy is markedly enhanced by combining a chemotherapeutic drug using an antiangiogenic schedule of drug dosing. These mAbs should show stronger antitumor efficacy in patients whose tumors depend entirely on human blood vessels.

Establishment of ascitic tumor of human pre-B acute lymphoblastic leukemia in nonconditioned nude mice.

In the present study, an ascitic tumor of NALM-6, a human pre-B acute lymphoblastic leukemia cell line, was established in nude mice which had not been subjected to any preconditioning such as X-irradiation and/or splenectomy. The ascitic tumor was also established in X-irradiated mice. Under various conditions, the tumor transplantability was 100%. NALM-6 cells were initially inoculated i.p. into 8-day-old nude mice after being admixed with X-irradiated HT-1080, a human fibrosarcoma cell line. Then, the in vivo grown (for 10 wk) tumor cells were serially transplanted i.p. into X-irradiated adult (10 to 12 wk old) nude mice. After the serial passages, we succeeded in establishing a highly transplantable NALM-6 ascitic tumor in nonpreconditioned as well as X-irradiated nude mice without the addition of HT-1080 cells. The ascitic tumor cells do not lose transplantability after in vitro culture for 20 days. Cellular radioimmunoassay and fluorescence-activated cell sorter analysis indicated that the in vivo established NALM-6 tumor cells retained the antigenic phenotype of the parental NALM-6 cells. Titration experiments revealed a reciprocal relationship between survival time of the mice and the number of tumor cells inoculated. When appropriate numbers of tumor cells (e.g., 4 x 10(6) cells) were used for the inoculation, survival times of individual mice fell within a relatively narrow range; this narrow range will facilitate the experiments where the present tumor model is used for evaluating the in vivo efficacy of antitumor agents. The present ascitic tumor models, particularly the one established in nonpreconditioned nude mice, will be useful for evaluating the in vivo efficacy of anti-human leukemia agents as well as for studying the in vivo biological behavior of the transplanted leukemia cells.

Unique epitopes of common acute lymphoblastic leukemia antigen detected by new monoclonal antibodies.

In the present study we have generated four new monoclonal antibodies (mAbs), termed SN5, SN5a, SN5b, and SN5c, which are directed toward the human common acute lymphoblastic leukemia antigen (CALLA). SN5 and SN5c were generated separately by immunizing two mice with a leukemia antigen preparation isolated from uncultured non-T-/non-B-acute lymphoblastic leukemia cells whereas SN5a and SN5b were generated by immunizing a third mouse with intact KM-3 (a cultured non-T-/non-B-acute lymphoblastic leukemia cell line) cells. It was found that the binding activities of mAbs SN5 and SN5c generated by using an isolated leukemia antigen preparation were approximately twice as large as those of mAbs SN5a and SN5b generated by using intact leukemia cells. All four of the present mAbs induced antigenic modulation of CALLA on the leukemia cells in vitro; subclasses of mAbs appear to be an important factor which influences the kinetics of antigenic modulation. SN5, SN5a, and SN5c immunoprecipitated a distinct Mr 100,000 component from detergent-solubilized cell membrane antigens but SN5b failed to do so. These four mAbs together with J5, another anti-CALLA mAb, were individually tested in a solid phase radioimmunoassay for reactivity with the detergent extracts of various human tissues, i.e., kidney, lymph node, spleen, brain, liver, pancreas, lung, and heart. SN5, SN5a, SN5c, and J5 showed reaction only with kidney whereas SN5b did not show significant reaction with any tissues including kidney. However, SN5b as well as SN5 showed a significant reaction with kidney in an immunoperoxidase-staining test. These results indicate that the interaction of SN5b with a unique epitope on the CALLA moleucle is strongly disturbed by relatively mild detergents (deoxycholate, taurocholate, and Nonidet P-450). These detergents did not significantly disturb the reaction between other mAbs (SN5, SN5a, and SN5c) and the corresponding epitopes on the CALLA molecule. Competitive binding experiments show that the three epitopes recognized by SN5, SN5b, and SN5c are sufficiently close to each other to allow complete or nearly complete reciprocal inhibition of binding to CALLA present on leukemia cells. Peculiar inhibition patterns, however, were observed between SN5a and the other three mAbs. SN5, SN5b, and SN5c inhibited only partially the subsequent binding of SN5a to the leukemia cells. Conversely, SN5a inhibited nearly fully the subsequent bindings of SN5, SN5b, and SN5c. These results suggest another unique epitope defined by SN5a.(ABSTRACT TRUNCATED AT 400 WORDS)

Establishment of new SCID and nude mouse models of human B leukemia/lymphoma and effective therapy of the tumors with immunotoxin and monoclonal antibody: marked difference between the SCID and nude mouse models in the antitumor efficacy of monoclonal antibody.

BALL-1, a human B leukemia/lymphoma cell line, was transplanted into nude and SCID mice under various conditions. The transplantation was substantially improved by preadaptation of BALL-1 by serial passages in newborn and young nude mice. We were able to establish the desirable conditions where 100% of SCID and nude mice that were inoculated i.p. with various doses of the adapted BALL-1 (termed BALL-1a) developed tumors. Tumors in SCID mice were disseminated to various tissues in a manner analogous to tumors in patients with B leukemia/lymphoma, whereas tumors in nude mice were not as widely disseminated and grew mainly as ascites. Flow cytometric analyses showed that all of the 11 tested cell surface markers of the parental BALL-1 were well maintained on the tumor cells recovered from the SCID and nude mice. The utility of the developed tumor models for the therapeutic studies was investigated by i.p. or i.v. administration of an anti-B leukemia/lymphoma monoclonal antibody, termed SN7 (IgG1 kappa), and SN7 immunotoxin (IT) that was prepared by conjugating SN7 to ricin A chain (RA) or deglycosylated RA (dgRA). In the nude mouse model study, SN7-RA that had been administered i.p. suppressed the tumor growth completely in all of the treated mice (n = 5) without any sign of tumor or undesirable side effects for as long as followed (i.e., 350 days), whereas unconjugated SN7 showed only a slight therapeutic effect. A control RA conjugate was not effective. In the SCID mouse model studies, several sets of experiments were carried out by i.p. or i.v. administration of IT, monoclonal antibody, or control IT. In the first three sets of experiments, SCID mice inoculated with 1.1 x 10(6) BALL-1a cells received an i.p. administration of phosphate-buffered saline or three different doses (i.e., 4 x 10 micrograms, 4 x 20 micrograms, and 4 x 30 micrograms) of therapeutic agents (SN7-RA and SN7). Virtually an identical result was obtained from the three experiments. All of the phosphate-buffered saline control group mice (n = 15) died within 35 days post tumor inoculation. In contrast, all of the mice that were treated with SN7-RA (n = 19) or with SN7 (n = 15) survived for as long as followed (i.e., 250 days). However, the unconjugated SN7 was less effective than SN7 IT for tumor suppression in SCID mice that were inoculated with a larger tumor burden (i.e., 4 x 10(7) BALL-1a cells).(ABSTRACT TRUNCATED AT 400 WORDS)

Development of a severe combined immunodeficiency (SCID) mouse model consisting of highly disseminated human B-cell leukemia/lymphoma, cure of the tumors by systemic administration of immunotoxin, and development/application of a clonotype-specific polymerase chain reaction-based assay.

A new severe combined immunodeficiency (SCID) mouse model consisting of highly disseminated human B-cell leukemia/lymphoma was developed by i.v. inoculation of BALL-1a, an in vivo adapted malignant B-cell line. A 100% transplantability was achieved in nonpreconditioned SCID mice using various BALL-1a doses between 2.5 x 10(4) and 6 x 10(6) cells. Hind-leg paralysis preceded the death of the mice. Utility of the developed tumor model for the therapeutic studies was investigated by i.v. administration of an anti-B-cell monoclonal antibody SN7 (IgG1) and its conjugate with deglycosylated ricin A chain (dgRA). The therapy was initiated 2, 4, or 6 days after tumor inoculation using 4 x 24 microg of SN7-dgRA or 4 x 20 microg of SN7; the total dose (96 microg) of SN7-dgRA corresponded to 14% of the LD50 dose. SN7-dgRA showed a strong antitumor efficacy in all groups of treated mice. All of the day-2 group mice (n = 7) and six (66.7%) of the day-4 group mice (n = 9) survived healthily for as long as followed (240 days), whereas four (57.1%) of the day-6 group mice (n = 7) survived healthily for as long as followed (200 days). Unconjugated SN7 showed a significant antitumor efficacy but was less effective than SN7-dgRA. A PCR-based assay specific for the clonogenic BALL-1a tumor was developed and applied to determine tumors in various organs of BALL-1a-bearing SCID mice. The assay was highly sensitive in screening for trace quantities of residual tumors in various organs of SCID mice, and it could detect 1 malignant cell/2.5 x 10(5) tissue cells. The PCR-based assay was shown to be much more powerful than the conventional histological analysis in detecting residual tumors. Furthermore, we could estimate quantities of the detected tumors by the PCR-based assay. It is remarkable to find that all examined organs of some of the SN7-dgRA-treated mice were tumor-free as determined by the clonotype-specific PCR-based assay. The present results show the usefulness of the newly developed SCID mouse model, SN7-dgRA, and the clonotype-specific PCR-based molecular assay for the study of therapy of human B-cell leukemia/lymphoma.

Lactoperoxidase-catalyzed iodination of human IgM. Differences between 7 S IgM and 19 S IgM and between cell surface 7 S IgM and serum 7 S IgM.

We have studied the lactoperoxidase-catalyzed iodination of human IgM and have measured the ratio of radioactivity incorporated into the mu chain to that incorporated into the L chain (i.e. the mu/L ratio). Both 7 S and 19 S IgM were examined. The ratio of radioactivity was found to be larger for 7 S IgM than for 19 S IgM for all four of the monoclonal IgM proteins examined. The data suggest that some tyrosines of the mu chain which are buried and not available for iodination in 19 S IgM become exposed on conversion of 19 S IgM to 7 S IgM. The mu/L ratio for the IgM found on the cell surface of RPMI 8392 cells was significantly smaller than the ratios for all of the five 7 S IgM proteins studied in solution. It appears, therefore, that a portion of the mu chain of the cell surface IgM of the RPMI 8392 cells is buried in the membrane.

The effect of adjacent residues on the reactivity of tyrosyl with iodine.

The effect of the adjacent amino acid side chain groups on the iodination rate of the tyrosine was studied. The model peptides used were Gly-Tyr-Gly, Leu-Tyr-Leu, Glu-Tyr-Glu, and Lys-Tyr-Lys, in which the tyrosine is sandwiched between two hydrophobic, two negatively charged, or two positively charged residues. The results show only minor differences in the iodination rate of tyrosine in these four peptides. These differences are very small in comparison with those previously observed between the tyrosines of kappa Bence-Jones proteins.

Expression of the immunoglobulin-associated protein B29 in B cell disorders with the monoclonal antibody SN8 (CD79b).

We studied the expression of the immunoglobulin-associated membrane protein B29 in 499 cases of chronic B cell diseases using the monoclonal antibody SN8 (CD79b). SN8 was positive in 5% (17/330) of chronic lymphocytic leukemia (CLL) and 100% (15/15) of B prolymphocytic leukemia. The expression of B29 in other B cell disorders was, as a rule, significantly higher than in CLL. Two thirds of non-Hodgkin's lymphomas in leukemic phase were SN8 positive, including lymphoplasmacytic (45%), follicular (83%), mantle cell (92%) and splenic lymphoma with villous lymphocytes (74%) while only 25% of hairy cell leukemias were SN8 positive. Within CLL, 2.3% of typical cases were SN8+ while 16% of cases with atypical morphology and an increased number of prolymphocytes were SN8+. Our results suggest a useful role for SN8 in the immunophenotypic differentiation of B cell disorders as a marker for non-CLL diseases. The analysis of B29 expression may throw light into the structure of the B cell antigen receptor in B cell malignancies while the distinctive reactivity profile of SN8 has direct applications to diagnosis.

Differential expression of B29 (CD79b) and mb-1 (CD79a) proteins in acute lymphoblastic leukaemia.

CD79 is a heterodimeric molecule comprising two polypeptide chains, B29 (CD79b) and mb-1 (CD79a). It is physically linked in the surface of B cells to membrane immunoglobulin, forming the B cell antigen receptor complex. Expression of the mb-1 (CD79a) chain has been studied in leukaemias and shown to be present in most B lineage acute lymphoblastic leukaemias (ALL). In contrast, little is known about the expression of B29 (CD79b) in this condition. Two monoclonal antibodies (MoAb) were used in this study by immunocytochemistry and flow cytometry: HM57, against an intracellular epitope of the mb-1(CD79a) chain, and SN8, reacting with an extracellular epitope of B29 (CD79b). Our aim was to investigate the expression of B29 (CD79b) in the various immunological subtypes of B lineage ALL and compare its cytoplasmic and membrane expression. Seventy-nine cases were studied, including 13 chronic myeloid leukaemia in B lymphoid blast crisis (CML-BC) and 66 ALL, subclassified as early B (two), common (28), pre-B (23), mature (five) and biphenotypic with B lymphoid commitment (eight). Most cases expressed mb-1 (CD79a) in the cytoplasm. B29 (CD79b) was expressed in the cytoplasm in 65% (15/23) of pre-B-ALL and in 14% (4/28) common-ALL but it was detected in the cell membrane in only three cases of mature B-ALL, being negative in all other B lineage subtypes ALL. Three of the biphenotypic leukaemias coexpressed cytoplasmic B29 (CD79b) and mu-chain. This was also seen in two cases of CML-BC, while four cases expressed only cytoplasmic B29 (CD79b) without mu-chain. Our results suggest that during B cell differentiation, B29 (CD79b) is expressed later than mb-1 (CD79a) in the cytoplasm and parallels the cytoplasmic expression of mu-chain. B29 (CD79b) is present in the membrane at a later stage compared to its cytoplasmic expression and found in mature B blasts (B-ALL) that express membrane Ig as it is in normal and leukaemic B lymphocytes.

Long-lasting complete inhibition of human solid tumors in SCID mice by targeting endothelial cells of tumor vasculature with antihuman endoglin immunotoxin.

In the present study, we developed an antitumor immunoconjugate that appears to be promising as a novel curative antitumor agent against a variety of human solid tumors. We generated a new antihuman endoglin (EDG) monoclonal antibody (mAb) K4-2C10 (or termed SN6f) that cross-reacts with mouse endothelial cells. Such cross-reactive anti-EDG mAbs have not been reported previously. This mAb was used to target tumor-associated vasculature in SCID mice inoculated with human tumors. No anti-EDG mAb or its immunoconjugates have previously been successfully used for targeting vasculature in vivo. In this study, MCF-7 human breast cancer cells were inoculated s.c. into SCID mice. K4-2C10 did not react with the MCF-7 cells but showed a weak reactivity with mouse endothelial cells. The mAb reacted with the proliferating endothelial cells more strongly than with the quiescent endothelial cells. The mAb exhibited much stronger reactivity (>10-fold) with human endothelial cells than with mouse endothelial cells and reacted strongly with vascular endothelium of tumor-associated blood vessels in a variety of human malignant tissues. Conjugates of K4-2C10 with ricin A chain (RA) and deglycosylated ricin A chain (dgRA) showed a weak but specific cytotoxic activity against murine endothelial cells in vitro; the 50% inhibitory dose of the RA and dgRA conjugates was 54 nm and 29 nm, respectively. Remarkable antitumor efficacy was observed when a small amount (a total of 60 microgram corresponding to 24% of the LD50 dose) of the dgRA conjugate was administered i.v. into SCID mice that had been inoculated s.c. with MCF-7. Unconjugated mAb K4-2C10 was not significantly effective in the inhibition of the tumor growth. The immunotoxin (IT) completely inhibited growth of the tumor in all of the treated mice (n = 8). Furthermore, similar antitumor efficacy was observed when the IT was administered i.v. into the tumor-inoculated SCID mice that had been pretreated with unconjugated K4-2C10 to block the potentially available weak binding sites of normal tissues. The strong therapeutic effects of the IT were reproduced in another set of therapeutic experiments. No significant side effects were observed in the mice. The differences in the tumor growth between the control group and the IT-treated groups were statistically significant. The IT showed antiangiogenic activity in the dorsal air sac method. The results indicate that K4-2C10 IT effectively treated the tumor-bearing mice by selectively inhibiting the tumor-associated blood vessels and by disrupting tumor-associated angiogenesis. The strong antitumor efficacy of the K4-2C10 IT is remarkable in view of the fact that K4-2C10 and its IT showed only a weak reactivity with mouse endothelial cells, and a relatively small amount of the IT was administered i.v. to treat s.c. tumors. We anticipate that the K4-2C10 IT will show much stronger antitumor efficacy and antiangiogenic activity in patients with solid tumors and other angiogenesis-associated diseases. The present results demonstrate for the first time that an anti-EDG mAb or its immunoconjugate can effectively target tumor-associated vasculature in vivo.

Association of serum endoglin with metastasis in patients with colorectal, breast, and other solid tumors, and suppressive effect of chemotherapy on the serum endoglin.

In this report, we present data indicating that the increased serum endoglin (EDG; CD105) quantitated by a double-antibody sandwich assay is associated with metastasis in patients with solid tumors including colorectal and breast carcinomas. In addition, we show that chemotherapy exerts a suppressive effect on the serum EDG. EDG is a proliferation-associated cell membrane antigen of human vascular endothelial cells. Furthermore, EDG is essential for angiogenesis. We generated two anti-EDG monoclonal antibodies (mAbs), termed SN6a and SN6h, defining different epitopes of EDG and developed a double-antibody sandwich assay to quantitate serum EDG in patients with solid tumors. SN6h possesses an exceedingly high antigen-binding avidity (K, 1.38 x 10(11) liters/mol), whereas SN6a possesses an ordinary avidity for a mAb directed to a cell surface antigen (K, 2.85 x 10(8) liters/mol). We measured serum samples from 101 patients with solid tumors (34 colorectal cancers, 16 breast cancers, and 51 other cancers), 8 patients with benign diseases, and 31 healthy volunteers. The serum level of EDG was significantly elevated in the patients with metastatic cancers. The mean serum EDG in the 42 metastasis-negative patients was 34.0 +/- 26.8 ng/ml (median value, 27.9 ng/ml), whereas the value in the 59 metastasis-positive patients was 63.8 +/- 72.5 ng/ml (median value, 37.2 ng/ml). The difference in EDG levels between the two groups was statistically significant (P = 0.012). Of the colorectal cancer patients, the difference in EDG levels between the 19 metastasis-negative patients and the 15 metastasis-positive patients was statistically significant (P = 0.02). In addition, the difference between the normal control (n = 31) and the 15 metastasis-positive colorectal cancer patients was statistically significant (P = 0.04). Of the breast cancer patients, the difference in EDG levels between the 11 metastasis-positive patients and the normal control was statistically significant (P < 0.005). In additional studies, we found that chemotherapy suppressed serum EDG levels in cancer patients. Of the 54 metastasis-positive patients with solid tumors, the mean serum EDG in the 32 chemotherapy-receiving [chemotherapy(+)] patients was 44.7 +/- 41.9 ng/ml (median value, 36.1 ng/ml), whereas the value in the 22 chemotherapy(-) patients was 102.4 +/- 99.5 ng/ml (median value, 64.8 ng/ml). The difference in serum EDG between the two groups is statistically significant (P < 0.005). In the majority of metastasis-positive patients who were not receiving chemotherapy, serum EDG was elevated. The results suggest that serum EDG may be a useful marker for monitoring early signs of metastasis and cancer relapse in a long-term follow-up of solid tumor patients.